#include <stdio.h>  
#include <math.h>  
  
int main() {  
    int n, cnt = 0;  
    if (scanf("%d", &n));  
    while (++cnt) {  
        if (cnt * (cnt + 1) / 2 >= n) {  
            printf("%d\n", cnt);  
            break;  
        }  
    }  
    return 0;  
}  